"The $10 bill, as everyone knows, features President Alexander Hamilton — undeniably one of our greatest presidents," a release from the company explained.

The problem, of course, is Hamilton not only wasn't a great president; he was never president at all.

In his e-mailed statement, though, Roberts says the promotion wasn't a mistake but part of an intentional effort to spark reaction.

"We started with the understanding that there's nothing people like more that pointing out that someone else is wrong. In fact, they like it so much they don't really stop to think about whether it was on purpose.

"But we were pleased some of the more savvy followers enjoyed the joke," the e-mail continued, saying also that the reaction was "pretty much in line with what we expected."

Groupon's promotion sparked buzz on Twitter and a number of news reports about the company and its misread of American history.